1. Field of the Invention:
The field of the Invention is computer systems utilizing hierarchical file structures, such as the hierarchical file structure used in the UNIX operating system environment.
2. Art Background:
Computer systems available today range in cost and sophistication from low cost micro-processor personal computers to sophisticated, high cost mainframe computers. However, the computer systems can be said to include the same basic components: at least one central processing unit (CPU) which controls the performance of computer operations, input/output units which control the input and output of information within and out of the computer system, and memory or storage space which stores information used by the CPU to perform computer operations.
The CPU is controlled by the operating system which dictates how certain computer operations are to be performed. One portion of the operating system is the file system module which determines and controls the file structure in the computer system.
One type of file structure in use is referred to as a hierarchical file structure. In a hierarchical file structure files are organized into a tree structure commencing with a single root node often referred to as the "root". One or more nodes may then be connected to the root and one or more nodes may be connected to each node. Every non-leaf node of the file system structure, that is a node which has another node connected to it, is a directory of files; and the files at the leaf nodes of the tree are either directories, regular files, or a special type of file such as a device file.
In a particular hierarchical file system, the name of this file is the path name that describes how to locate the file in the system hierarchy. A path name is a sequence of component names separated by the "/" character. A full path name starts with a "/" character which specifies that a file is found by starting at the file system root and traversing the file tree, following the branches that lead to successive paths. For example, the path name /usr/src/cmd/two.c follows a path such as that shown within the box in FIG. 1 and designates the two.c file labeled 5 in the tree shown.
In the software development environment, numerous computer programmers may be working concurrently on a single program or a group of programs which are interrelated and operate together. It is quite desirable that the work be done simultaneously so that it may be completed in the shortest amount of time. Typically, each software programmer makes a copy of those files in the portion of the file structure he is working in and works on those particular copies to achieve his goal. Thus, if a product consists of twenty programs, each programmer may have a copy of those twenty programs in his user area.
The problem with this arrangement is that each programmer must usually work with a large number of files in order to work on a single file. Consequently, multiple copies of these files exist in numerous places on the system, requiring a large amount of disk memory space and adding to the complexity of the arrangement and the identification of the files. Furthermore, it is quite easy to lose track of or confuse older versions of programs with the current versions of programs. For example, programmer one may be working on certain portions of a program that has a revision date of may, and programmer two may be working on a program that has a revision date of June. Thus the changes made by either programmer are contained in different versions; and, in order to incorporate the new software developed by the programmers, the code must be incorporated into the latest version of the code, a repetitive and cumbersome task.